Stabilizing Sowashee Creek and Repairing a Sanitary Sewer Interceptor in Mississippi

In Meridian, Mississippi, a 54-inch diameter sanitary sewer interceptor collapsed due to erosion along the Sowashee Creek bank. In partnership with the City of Meridian, Kimley-Horn designed an innovative solution that realigned the existing interceptor and stabilized the creek bank to protect the wastewater infrastructure in the future. We provided the following services on this project:

• Pipeline design
• Creek bank restoration/stabilization
• United States Army Corps of Engineers permitting for wetland disturbances and creek bank restoration (in partnership with a subconsultant)
• Mississippi Department of Transportation (MDOT) permit preparation and negotiation
• Easement negotiations

Stabilizing Solutions for the Creek Bank

After the interceptor collapsed, our team immediately coordinated with the City for installation of a temporary bypass pumping system. Then, we evaluated options to prevent erosion from impacting the pipeline replacement in the future, including using a sheet pile wall or realigning the pipe away from the creek. However, subsurface soil conditions were not conducive to sheet pile wall installation, and nearby railroad tracks limited how far the interceptor could be moved away from Sowashee Creek.

Ultimately, we replaced 405 feet of 54-inch diameter pipeline slightly away from the creek and leveraged boulder toe creek bank restoration—which protects the interceptor by stabilizing the bank and establishes native vegetation on the restored slope. This method was new to our client, and we operated as their trusted advisor with this stabilizing solution. Due to the constrained location, we also worked closely with the City of Meridian and MDOT to obtain a temporary access permit allowing for the construction of a short-term road under the interstate bridge for site access.

Overcoming Construction and Supply Chain Challenges

To support the boulder toe construction solution and find materials that were not available in Mississippi, we reached out to our Kimley-Horn partners in North Carolina. They connected us to out-of-state contractors, who educated the in-state contractors about this restoration solution. A local precast concrete company then manufactured concrete boulders to stabilize the toe of the creek bank. We also coordinated with pipe suppliers to identify readily available, cost-effective materials during a time of significant price fluctuations and supply chain disruption.

In addition to showcasing the power of partnership and cross-state collaboration, this interceptor replacement project stopped raw sanitary sewage from flowing into Sowashee Creek and provides the Meridian community with reliable sanitary sewer infrastructure.